Various communication standards require power amplifiers to have multiple power modes to obtain the best power efficiency in each mode and to decrease power consumption in power modes that require less power. A common technique for providing amplification in different power modes is to use multiple amplifiers. However, current techniques that employ multiple amplifiers often result in performance degradations since the different amplifiers tend to load one another. Alternatively, a single amplifier can be used with a DC/DC converter to dynamically adjust the amplifier supply voltage. Unfortunately, this is an expensive solution that adds significant size and cost.
Thus, inexpensive multi-power mode amplifiers are needed that do not suffer significantly from additional loading.